build(frontend): close the lint gaps the E32 audit measured

eslint now also enforces:
- the React Compiler diagnostics that `recommended` leaves out (todo,
  memo-dependencies and ten zero-hit tripwires);
- a description on every suppression, and no blanket disables;
- no focused or skipped tests (vitest and playwright);
- the typed pair no-floating-promises and no-deprecated.

Lint also covers e2e/ and the TypeScript build configs, which `eslint .`
had been skipping in silence.

Every hit is fixed or suppressed inline with a named reason:
- The 31 try statements the compiler cannot lower yet carry a suppression
  until S3 rewrites them. Five other compiler skips were plain fixes:
  a module counter bumped inside a hook, a ref read in a default
  parameter, and a local named like the <section> it renders.
- The real defects behind floating promises are fixed. ChatDock threw at
  nobody when the device key store could not be opened. VideoEditor's
  play() rejection went unhandled. loadYouTubeApi never rejected, so a
  blocked IFrame API left the player on an empty stage forever; it now
  fails on a script error or after 15 s, shows its own error with the
  way out, and lets the next open try again.
- MutableRefObject, FormEvent and lucide's deprecated brand icon are
  replaced. The YouTube glyph now lives in lib/brandIcons.
- The lint-probe harness lets its virtual file names into TypeScript's
  default project, so the contract tests still run the real config.

frontend/src/components/PlaylistsRail.tsx

@@ -2,7 +2,8 @@ import { useCallback, useEffect, useMemo, useRef, useState } from "react";
 import { useTranslation } from "react-i18next";
 import { useMutation, useQuery, useQueryClient } from "@tanstack/react-query";
 import { qk } from "../lib/queryKeys";
-import { ListVideo, Pin, Plus, RefreshCw, Youtube } from "lucide-react";
+import { ListVideo, Pin, Plus, RefreshCw } from "lucide-react";
+import { YouTubeIcon } from "../lib/brandIcons";
 import { api, type Playlist } from "../lib/api";
 import { compareText } from "../lib/collate";
 import { formatRuntime } from "../lib/format";
@@ -155,6 +156,7 @@ export default function PlaylistsRail({
   async function syncYoutube() {
     if (syncing) return;
     setSyncing(true);
+    // eslint-disable-next-line react-hooks/todo -- the React Compiler cannot lower try/finally yet, so the enclosing component or hook stays uncompiled; pinned in compilerCoverage, burned down in E32 S3
     try {
       const r = await api.syncYoutubePlaylists();
       qc.invalidateQueries({ queryKey: qk.playlists() });
@@ -360,7 +362,7 @@ export default function PlaylistsRail({
                       <div className="flex items-center gap-1 text-[0.8125rem] text-fg">
                         <span className="truncate">{plName(pl)}</span>
                         {(pl.source === "youtube" || pl.yt_playlist_id) && (
-                          <Youtube
+                          <YouTubeIcon
                             className={`w-3 h-3 shrink-0 ${pl.dirty ? "text-accent" : "text-muted"}`}
                           />
                         )}